Prior to WWII, the German Army realized the need for a self-propelled direct-fire support weapon for their motorized infantry and armor formations. Many of the artillery pieces in the German Army were cumbersome to deploy and could not keep up with modern units in the field. Even after the war started, much German artillery was still horse-drawn. One of the first attempts to provide the new German Army with self-propelled artillery was the sIG 33. This unit saw action in Europe, North Africa and Russia.

15cm (150mm) sIG 33 auf GwI Ausf B

The sIG 33 15cm infantry gun fired a 63 pound (29kg) shell at 240 meters per second, with a range of 4,700 meters. The 15cm gun, introduced in 1936, was capable of firing high explosive (HE), chemical, and anti-armor “stick bomb” rounds. The "stick bomb" functioned like a large rifle grenade. It had a range of 1.2 km, was highly inaccurate, and had to be muzzle loaded. The round was generally used against static targets, such as fortifications, because it simply couldn't hit anything else.

The first sIG 33 -- sIG 33 (SF) auf PzKpfw I Ausf B or sIG 33 Pz IB for short -- was a sIG 33 field gun mounted, complete with wheels and undercarriage, on an unmodified Panzerkampfwagen IB (Pz IB) tank chassis. A gun shield made of 10 mm steel plates provided protection for the crew, although it was open to the top and rear. The gun could elevate from -4 to +75 degrees and traverse 12.5 degrees left and right of center. Alkett made 38 of these vehicles, which were fielded in January and February of 1940.

The sIG 33 Pz IB was powered by a Maybach NL 38TR, 6-cylinder gasoline engine. It was necessary to use a gasoline engine because experimentation showed that diesel engines were not powerful enough to move the gun which, at 8.5 tons, was extremely heavy. This engine could generate 100 hp at 3,000 rpm. The vehicle carried about 145 liters of fuel, which gave it a cruising range of approximately 145 km and a road speed of 35km/hr. The transmission had four forward and one reverse gear.

Unfortunately, the configuration allowed minimal stowage, so the vehicle carried only three rounds and a crew of three. Another crewman followed in a separate vehicle, which also carried an additional 25 rounds and the crew’s personal gear.

The weight of the armor shield and gun made the vehicle top heavy and resulted in poor cross-country mobility. These factors also contributed to accelerated wear and tear on the vehicle’s suspension.

The last sIG 33 Pz IB was taken out of service in Russia in 1943.

Simultaneously, Alkett also produced twelve sIG 33 (SF) auf Fahrgestell PzKpfw II self-propelled guns for duty in North Africa. This version had a Maybach HL62 TRM 6-cylinder gasoline engine and a transmission with six forward gears and one reverse. The gun was the same as earlier versions, but the chassis was a PzKpfw II tank chassis. This version’s gun could only elevate to +50 degrees, though the traverse range remained the same. It had a cruising range of 160 km with a speed of up to 40 km/hr. This version weighed 11.5 tons and carried 25 rounds and a crew of four. Though intended to support operations around Tobruk, the vehicle was awkward to maneuver in the desert sand and was unable to provide effective fire support. The Egyptian Army used the last three working versions of these SP guns during combat operations in 1948 and 1949.

Late in the war, the Germans fielded the sIG 33B. It had a crew of five, carried 30 rounds, and weighed 21 tons. This SP artillery piece had a 150 mm Stu I G gun and included a 7.92 mm MG 34 machinegun with 600 rounds. It was powered by a Maybach HL 120 TRM V12 gasoline engine with a six-speed transmission. This engine was capable of 300 horsepower at 3,000 rpm. It carried 320 liters of fuel and had a cruising range of 110 km. The gun on this version could traverse only 3 degrees left or right of center and elevated from -3 degrees to +25 degrees.